One-piece hollow steel propeller



May 26, 1936. w. s. HOOVER ONE-PIECE HOLLOW STEEL PROPELLER Filed Oct. 27,- 1951 2 Sheets-Sheet l 4 v iitfii nlllllin v v INVENTOR. m .5 NM 31 7 '6' A TTORNE Y.

y 1 w. s. HOOVER ONE-PIECE HOLLOW STEEL PROPELLER Filed Oct. 27, 1931 i2 SheetS- -Sheet 2 A TTORNE Y.

Patented May 2 ,1936

UNIT

This invention relates to improvements in hollow steel or duralumin propeller blades and it is among the objects thereof to construct hollow metallic blades by the steps of forming a blank by die stamping and shearing operations,

rolling the blank to form a wall section of varying thickness from the blade root to the blade tip, shaping the blade=in a jig by means or a ing to a minimum stresses imposed on the welded seam and also permitting the use of thinner metal for the blade wall. 1

Another object 01' the invention is to provide a propellerv blade design which is interchangeable 25 with ground adjustable hubs.

ing of a hollow metal propeller blade bythe above designated steps from one piece of metal into a finished blade and which shall have its hub anchorage abutments integrally formed in the die forming operationof. the blade.

A still further object of the invention is the provision of hollow metal propeller blades of the above designated character which shall be of, ,great structural strength coupled with a minimum w ht ,to reduce to a minimum the centrifugal thrust load on the thrust bearing.

These and other objects of the invention will become more apparent from a consideration of the accompanying drawings constituting a part hereoi in which like reference nate like parts and in which:

Figurelisatopplanviewotadiestamped and sheared blank from which the improved form or propeller blade is made; V Figure 2 a side elevational view thereof showing the tapered wall section;

Figure 3 a top plan view of the shapingdie;

Figure 4 a longitudinal sectional view taken'on the longitudinally center line of the shaping die 9 shown in Figure 3;

Figure 5 a cross-sectional view of the hollow propeller blade shaped to its finished form;

Figure 6 aperspective view of the back of the finished blade showing the welded seam;

Figures 7 ion inclusive are cross-sectional.

Another object of the invention is the mak-- characters desig- 2,042,099 7 oNn-Pmcs HOLLOW STEEL rnornamn Walter S. Hoover, Girard, Pas assignor of one-- hall to Patrick H. Crow, Meadvilla l'a.

Application October 27, 1931, Serial No. 571,342

vs Claims. (Cl.170-'159) views of the hollow blade from the blade root to' the tip taken along the lines passing through the blade in the manner shown on Fig. 6 and correspondingly numbered; and Figure 13 an end elevational view of the blade tip. With reference to Figures 1 and 2 of the drawings, the reference character I generally designates a blank, die-stamped and sheared from an 2 which is cut out in the-manner shown to form the curved tip shown in Figure-6 of the drawings. 2-11. and 2b are the edges which form the seam of the finished blade and 2-'-c are cut-out portions to form the blade tip and along which the blank is bent to form the hollow blade structure.

A segment shaped opening 3 is cut out of the blank near the tip of the blade in the die stamping operation which constitutes a vent in the finished blade structure herein termed the reaction exhaust vent for scavaging the exhaust gases from the engine.

The wide end of the blade is notched at its edges as shown at 4 and is provided with hexagonally shaped perforations 5, the perforations being in alinement with the substantially V- shaped notches 4 of the edge of the blade. The purpose of the notches and perforations is to enable the metal to be pressed into the shape of anchorage abutting shoulders without distorting the metal along the welding seam of the blade. 7

As shown in Figure 2 of the drawings, the blank is of varying thickness, the wall thickness gradually tapering from the square end to the tip, this taper being produced by a suitable rolling operation.

By rolling the tapered wall section a thicker blade root wall is provided which must of necessitybe stronger and the reduced tapering wall section toward the blade tip reduces the weight of the blade.

In the blanking operation the tapered blank is placed under a stamping die and all unevenness of its edges are sheared oil to precision and uniform shape and the notches and perforations are simultaneously formed in the blank.

The finished blank is then placed in a jig and ashapingdiefil igureaispressedbymechaniover the edges of the blank to cause-themto overlap the shaping die, these overlapping portions forming the back of the blade while simultaneously with this bending movement the blade root is being stamped. out or pressed with its anchorage abutments I, Figures 5 and 6, these abutments being formed by the bending of the metal over the shoulders I, 9 and IQ of the shaping die, Figure 3.

The anchorage abutments 1, Figures 5 and 6 are in the shape of radial flanges with square faces Ia disposed to react against the propulsive thrust of the blade and are designed to prevent straightening of the metal in the blade root when permitted to sp g apart and the shaping die is removed, thus leaving the blanked metal shaped with its camber in the face or front of the blade, with the leading and trailing edges creased, and the anchorage abutments I pressed into shape.

The form blade is then brought together by bend-- ing down its free edges 2-a and 2-b to form a seam ii on the back of the blade along which the blade is welded to form an integral unit. The welded scam 12 extends from the end of the blade root to the tip of the blade and is designated by the heavy line in Figure 6 of the drawings. Similarly the reference character I! designated the weld in the views from Figures 7 to 11 of the drawings wherein the camber lla of the blade is also clearly shown.

By forming the hollow blade of one piece of flat metal gradually reducing in wall section from the root of the blade to the tip as described, and by joining the free ends of the formed blade by welding along the back of the blade, the welded seam is in a position parallel to the tip blade deflection at periods of synchronized vibration and is not subject to stress. The gradually tapering wall section of the blade eliminates any variation in structural strength from the rodt to the tip since it permits adding necessary strength in the blade root walls to withstand centrifugal force tending to shear the pressed-in anchorage abutments and to withstand the angular thrust or bending moments resulting from propulsion. As

- the angular thrust or bending moments diminish toward the blade tip, less strength is needed thus eliminating excess metal at the-tip end.

This design while providing greater structural strength also reduces to a minimum the weight of the propeller and renders it particularly suitable for installation in a variable pitch propeller mid portion of the back of the blade which is hub since it reduces to a minimum the centrifugal thrust load on the one direction thrust bearing resulting in longer life for this vital element.

By employing duralumin metal the de-sign will permit higher peripheral speed because 5 of the reduction in weight. Steel blades are preferable for military purposes as they are invulnerable to machine gun-fire. Steel will not shatter and may be perforated many times without destroying its function. 5

The design of the reaction vent 3 facilitates the straightening of damaged blade tipaltheopening being sufllcient to insert aflat tool and this type of vent'eliminates the pressure of the scavenged gases from adding to the bearing load of a varil5 able pitch propeller.

It will be evident from the foregoing description of the invention that the method of making propellers disclosed therein utilizes a single piece of metal which after shaping and welding be- 20 comes an integral unit of great strength which reduces to a minimum blade flutter and rapid herein set forth.

I claim:

l. A hollow propeller blade structure comprising a one-piece sheet metal blank varying in wall section from maximum thickness at the blade root to minimum thickness at its tip the longitudinal edges of which. are folded to constitute complementary abutments which are welded on the back of the blade at substantially the center thereof.

2. A hollow propeller blade structure comprising a one-piece sheet metal blank varying in wall section from maximum thickness at the blade root to minimum thickness at its tip the longitudinal edges of which are folded to constitute complementary 'abutments'forming a seam at the mid portion of the back of the blade said seam being welded, and said blade having anchorage abutments formed integrally in the blade root.

3. A hollow propeller blade structure comprising a one-piece sheet metal blank varying in wall section from maximum thicknessat the blade l root to minimum thickness at its tip the longitudinal edges of which are folded to constitute complementary abutments forming a seam at the joined by welding, and having anchorage abutments formed integrally in the blade root, said abutments having flat surfaces disposed to react against the propulsive thrust and having sloped faces to provide a maximum clamping area. WALTER S. HOOVER. 

